Method and apparatus for repairing turbine rotor

ABSTRACT

A method for repairing a rotor of a turbine includes providing a rotor having a groove portion defined by a circumferential portion of the rotor. The circumferential portion of the rotor is removed to create an opening to provide access to the groove such that the opening, immediately adjacent the groove, is narrower than the groove. A guide block may be extended into a receiving slot separating a first protruding surface from a second protruding surface of the rotor such that a weld area slot of the guide block extends over at least a portion of the opening. The opening may be welded adjacent the guide block to close at least a portion of the opening.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. Ser. No. 13/488,033 filed onJun. 4, 2012, which is a Divisional of U.S. Ser. No. 12/640,961 filed onDec. 17, 2009, now U.S. Pat. No. 8,245,475 issued on Aug. 21, 2012,which is a Divisional of U.S. Ser. No. 11/106,234 filed on Apr. 14,2005, now U.S. Pat. No. 7,690,111 issued on Apr. 6, 2010, the entiredisclosures of which are incorporated herein by reference.

TECHNICAL FIELD

This invention relates, in general, to turbines and, in particular, tosystems and methods for repairing rotors of turbines.

BACKGROUND ART

Turbine rotors often experience cracking requiring repair before the endof their design life due to the environment associated with suchturbines (e.g., high temperatures and/or pressures). For example, arotor 10 (FIG. 1) may experience cracking in at least two locations ator before half of the design life thereof is consumed. Such cracking mayoccur at the bottom of an L-Groove cooling slot formed in the rotor andat a fabrication weld formed in bridge rails thereof. The bridge railsmay support heat shields during operation of the turbine, which aremounted axially in openings between the bridge rails. Bottoms of theL-Grooves may experience cracking due to low cycle fatigue and poorgeometry. High local mechanical stresses resulting from the originalweld geometry of the bridge rails may cause premature low cycle fatiguecracking in the fabrication weld.

The cracks formed in such turbine rotors are conventionally repaired bymachining an opening 300 in a circumferential portion 310 of the rotorwhich is the same width as a top end of an L-Groove 320 as depicted inFIG. 2. In particular, any cracks in circumferential portion 310 (e.g.,in a fabrication weld thereof) or at a bottom end 321 of L-Groove 320may be removed by machining through the opening created. After machiningthe cracks from groove 320, the groove may be closed by welding theopening shut. The location of a conventional weld does not allow agentle transition between the weld and sidewalls 330 of the groove.Instead, a sharp angle is formed at an intersection 340 between aconventional weld 331 and adjacent side walls of the groove. Such anabrupt transition created by such a conventional weld increases stressin the area of the weld and allows for premature failure. Further, sucha repair causes heat effected zones of the welds to be placed in suchstressed areas.

Thus, a need exists for an improved method for repairing cracks inturbine rotors.

SUMMARY OF THE INVENTION

The present invention provides, in a first aspect, a method forrepairing a rotor of a turbine which includes providing a rotor having agroove defined by a circumferential portion of the rotor. The methodfurther, includes removing a part of the circumferential portion of therotor to create an opening to provide access to the groove such that theopening immediately adjacent to the groove is narrower than the groove.

The present invention provides, in a second aspect, a method for use inclosing an opening in an object having a plurality of protrudingsurfaces forming an intermittent geometry. The method includes extendinga guide block into a receiving slot separating a first protrudingsurface from a second protruding surface of the object such that a weldarea slot of the guide block extends over at least a portion of theopening, The opening is welded adjacent the guide block to close atleast a portion of the opening.

The present invention provides, in a third aspect, a system for use inclosing an opening in an object having an intermittent geometry Whichincludes a member configured to be received in a receiving slot of theobject with the slot having an edge defining a side of the opening. Themember includes a central portion, at least one outer portion, and anouter surface. A core connects, the central portion and the at leastouter portion. At least one breakaway, cut includes a space separatingthe central portion and the at least one outer portion. The spaceextends from the core to the outer surface to allow the central portionto be separated from the at least one outer portion in response to thecore being removed.

The present invention provides, in a fourth aspect, a system for use inrepairing a groove of a rotor of a turbine which includes a lathe toolconfigured to extend through an opening in the rotor into the groove.The opening, immediately adjacent the groove, is narrower than thegroove. The lathe tool includes a shaping portion which is configured tocontact the wall of the groove to shape the groove in response to therotor being rotated in contact with the contacting portion.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter, which is regarded as the invention, is particularlypointed out and distinctly claimed in the claims at the conclusion ofthe specification. The foregoing and other objects, features, andadvantages of the invention will he apparent from the following detaileddescription of preferred embodiments taken in conjunction with theaccompanying drawings in which:

FIG. 1 is a perspective view of a turbine rotor;

FIG. 2 is a cross-sectional view of a prior art repair of the L-grooveof the rotor of FIG. 1;

FIG. 3 is a perspective cross-sectional view of an L-Groove of the rotorof FIG. 1;

FIG. 4 is a side cross-sectional view of the L-groove of FIG. 3;

FIG. 5 is a side cross-sectional view of a lathe tool inserted in thegroove of FIG. 3 and being utilized to form a curved portion connectingan opening and sidewall of the groove;

FIG. 6 is a side cross-sectional view of a lathe tool inserted in thegroove of FIG. 3 and being utilized to form a side wall of the groove;

FIG. 7 is a perspective view of a lathe tool utilized to form a bottomcorner of the groove of FIG. 3;

FIG. 8 is a cross-sectional view of the L-groove of the rotor of FIG. 1after removing cracks in the rotor and closing an opening in the rotor;

FIG. 9 is an enlarged side cross-sectional view of an upper end of theL-groove of FIG. 8 with an opening therein prior to the opening in therotor being closed;

FIG. 10 is a cross-sectional view of the enlarged portion of the rotorof FIG. 9 after the opening thereof has been welded closed;

FIG. 11 is a perspective view of a portion of the rotor of FIG. 3depicting one embodiment of the repair of the opening of FIGS. 8-10;

FIG. 12 is a perspective view of a guide block configured to receive inthe slots of the rotor of FIG. 11;

FIG. 13 is a perspective view of a backing band configured to bereceived in a weld area slot of the guide block of FIG. 12;

FIG. 14 is a side cross-sectional view of the guide block of FIG. 12attached to a retaining ring and inserted into one of the slots of FIG.11;

FIG. 15 is a side cross-sectional view of the guide block of FIG. 14having a backing band welded to the weld area slot thereof;

FIG. 16 is a perspective view of the guide block of FIG. 15 connected tothe backing band and retaining ring and inserted into a receiving slotof the rotor;

FIG. 17 is a side cross-sectional view of the guide block, backing band,and retaining rings of FIG. 15, and further including a weld build-up inthe weld area slot of the guide block;

FIG. 18 is a perspective view of the guide block of FIG. 12 furthershowing a core of the guide block connecting outer portions of the wideblock to an inner portion thereof;

FIG. 19 is a perspective exploded view of the guide block of FIG. 18after the core thereof has been machined away and the outer portionshave been separated from the inner portion;

FIG. 20 is a perspective view of an automatic Tungsten Inert Gas (TIG)welding system in the process of welding the rotor of FIG. 11;

FIG. 21 is a side view of a rotating machining tool utilized to machinethe rotor of FIG. 11 after welding closed the opening thereof;

FIG. 22 is a side perspective view of another rotating machining toolutilized to machine the rotor of FIG. 11 after welding thereof; and

FIG. 23 is a perspective view of a cylindrical member to be welded andguide blocks configured to be received in openings of the cylinder.

DETAILED DESCRIPTION

In accordance with the principles of the present invention, systems andmethods for repairing cracks in a rotor of a turbine and other objectshaving an intermittent geometry are provided.

As depicted in FIG. 3, a rotor 10 (FIG. 1) of a turbine (not shown)includes bridge rails 20 which extend radially outwardly and areseparated from one another and may have heat shields (not shown) axiallylocated in spaces between the rails during turbine operation, Asdepicted in FIG. 3, rotor 10 may include an L-Groove 30 having an axialportion 35 and a radial portion 40. Rotor 10 may be firmed of chromiummolybdenum type steel alloy, other steel alloys, or other such materialspreferred to be utilized in turbine environments. As depicted in FIG. 4,an initial fabrication of rotor 10 results in a weld 100 (e.g., afabrication weld) at a top or outer radial end of radial portion 40,After a period of use, radial portion 40 may develop upper cracks 50 ina portion of rotor 10 defining an upper end thereof (e.g., in weld 100)as depicted in FIG. 3, Lower cracks 60 may also occur at a bottom end 42of radial portion 40. For example, the configuration and orientation offabrication weld 100 and the effect of thermal fatigue on suchfabrication weld and the remainder of L-Groove 30 may result in cracks50 and cracks 60 after a period of use of rotor 10.

Upper cracks 50 and lower cracks 60, as depicted in FIG. 3, may weakenrotor 10 thereby causing a danger of failure thereof. Cracks 50 may beremoved from rotor 10 by machining away (e.g., via a metal lathe) orotherwise removing a circumferential portion 110 (e.g., a portion of onerail of bridge rails 20 adjacent and including weld 100) of rotor 10 tocreate an opening 120 (FIG. 9), thereby providing access to radialportion 40. For example, opening 120 (FIG. 9) may be created by rotatingrotor 10 and contacting circumferential portion 110 with a fixed, lathetool (e.g., any industry standard lathe tooling of a rigid or insertstyle) to cause circumferential portion 110 to be gradually removed asrotor 10 rotates against the lathe tool. Such rotation may also createadditional openings in other rails of bridge rails 20 to form acircumferential groove (e.g., circumferential groove 121, FIG. 11)around rotor 10.

Opening 120, immediately adjacent the L-groove (e.g., radial portion40), may be narrower than the groove as depicted in FIG. 9. For example,opening 120 may be narrower in a transverse direction relative to alongitudinal dimension of radial portion 40 than a width 130 of radialportion 40. Further, opening 120 may be formed offset (e.g., spacedfrom) sidewall 140 of radial portion 40. Sidewalls 140 may be machinedto result in curved portions 150 connecting side walls 140 to sides 125of opening 120. For example, curved portions 150 may have a curvature ofabout a ¼ inch diameter circle and opening 120 may be about ¾ inch widewhile width 130 may be about 1 inch. Sidewalls 140 and curved portions150 may also be formed using lathe tools and by rotating rotor 10. Forexample, as depicted in FIG. 5, a curved portion 151 may be formedutilizing a lathe tool 200 extending through opening 120 as rotor 10rotates. FIG. 6 depicts a lathe tool 210 extending through opening 120and forming a portion of sidewalls 140.

Lathe tool 210 may include, for example, a main portion 215 and offsetportion 217. Main portion 215 is substantially aligned with opening 120and offset portion 217 is offset from main portion 215 and opening 210(i.e., misaligned relative to opening 210 and a longitudinal axis ofmain portion 215) to allow it to contact one of sidewalls 140 to formthe sidewalls in a particular desired geometrical configuration. FIG. 7depicts a lathe tool 131 which may be utilized to form a bottom corner46 (FIG. 8) of radial portion 40.

Lathe tool 131 may include a lathe tool insert 135 for shaping bottomcorner 46 (FIG. 8). Insert 135 may be a hardened and shaped bit which isattachable to tool 131 to allow a particular shape to be formed in abody (e.g., rotor 10) which are rotating in contact with insert 135.Also, tool 131 includes an offset portion 137 to allow insert 135 to belocated offset from opening 120 in a direction toward one of sidewalls140 to allow insert 135 to contact one of sidewalls 140, e.g., to formbottom corner 46.. As will be understood by one skilled in the art,lathe tools may be formed in any number of shapes and materials (e.g.,standard square stock steel) to allow the tools themselves or insert(s)attached thereto to contact any portion of sidewalls 140 or otherportion of L-groove 30 to allow sidewalls 140 or such other portion ofL-groove 30 to be shaped,

The use of a narrowed opening (e.g., opening 120, FIG. 9) offset (e.g.,spaced) from sidewalls of radial portion 40 to remove cracks in afabrication weld and to access a groove (e.g., radial portion 40 ofL-Groove 30) causes heat effected zones to be moved relative to aconventionally repaired weld (FIG. 2). In particular, the new weldlocation moves heat effected zones from a corner (e.g., intersection340. FIG. 2) where a bridge rail meets a vertical side wall of a radialportion of a groove (i.e., in a conventionally repaired weld) to curvedportions 150 connecting opening 120 to sidewalls 140 as depicted in FIG.9, for example.

The creation of opening 120 as described differs from a conventionalmethod for removing cracks, as depicted in FIG. 2 and described above.In particular, such prior method includes creating opening 300 incircumferential portion 310 such that opening 300 has a substantiallysame Width as a portion of groove 320 located immediately adjacentthereto. Because the opening created via such prior method has the samewidth as the portion of the groove immediately adjacent thereto, thereis no gentle transition between weld 331 which fills opening 300 andgroove sidewalls 330. Instead, sharp angles are present at intersections340 between weld 331 and sidewalls 330. Such abrupt transitions due tothe sharp angles at intersections 340 increase stress in the area of theweld and allows for premature failure (e.g., cracking) as describedabove. Further, heat effected zones of the weld are located in suchhighest stressed areas at these abrupt transitions. In contrast, curvedportions 150 as described above and depicted in FIGS. 9-10 for example,allow a gentle slope (e.g., at curved portions 150) between sidewalls140 and weld 160. Accordingly, the curved shape of curved portions 150along with the corresponding narrowed opening (e.g., opening 120) lowerstresses during use of rotor 10 in the region of a top end 43 (FIG. 9)of radial portion 40 and circumferential portion 110, relative to aconfiguration of L-groove 320 in prior art crack removal methods asdepicted in FIG. 2, for example. This lowered stress due to the contourof curved portions 150 extends a future operating life of a bridge railportion 22 and bridge rails 20, for example.

Also, lower cracks 60 (FIG. 3) may be machined or otherwise removed frombottom end 42 of radial portion 40 by inserting one or more lathetool(s) as described above (e.g., using lathe tool 131) through opening120. Such machining of bottom end 42 removes cracks 60 and some materialof rotor 10 around cracks 60 to result in a new geometry of bottom end42. Such new geometry may be designed using finite element analysis toresult in a particular geometry suited for a particular rotor, therebyreducing a likelihood of future cracking, for example. Also, in oneexample, side walls 140 may be machined by metal lathe tools (e.g., tool210) inserted through opening 120 such that side walls 140 aresubstantially parallel to each other in a central portion 44 of radialportion 40 with central portion 44 including radial portion 40 slightlybelow opening 120 and slightly above axial portion 35 as depicted inFIG. 8.

As depicted in FIG. 11, a plurality of openings, such as opening 120,may extend circumferentially around rotor 10 to form a circumferentialgroove 121. After curved portions 150, bottom end 42. (FIG. 3) and/orside walls 140 (FIG. 4) of radial portion 40 (FIGS. 3-4) has beenmachined as described above (e.g., via lathe tools), it is necessary toclose circumferential groove 121 and thus opening 120, tear example bywelding. It is also desirable to return the outer surface (e.g., bridgerails 20) of rotor 10 to its original geometry to complete the repair.

In one example, circumferential groove 121 (FIG. 11), including opening120, may be closed utilizing a guide block 301 as depicted in FIG. 12.Guide block 301 may be configured (e.g., shaped and dimensioned) to beinserted into bridge rail slot 21 between adjacent bridge rails (e.g.,bridge rail 22 and bridge rail 23). Guide block 301 may span an entirelength of slot 21, Guide block 301 may be manufactured from a materialthat closely matches rail slot 21 of rotor 10 to minimize elementdiffusion contamination and migration during the welding processes to beperformed. The guide blocks are used to fill the space (e.g., rail slot21) between intermittent geometries (e.g., rails 20) of part(s) (e.g.,rotor 10) to be welded. Also, one or more backing bands (e.g., backingband 350 (FIG. 14)) may be utilized, in conjunction with such guideblocks to close an opening (e.g., opening 120) in such a rotor (e.g.,rotor 10). Backing Bands 350 may also be manufactured from a materialthat closely matches rail slot 21 of rotor 10 to minimize clementdiffusion contamination and migration during the welding, processes tobe performed. One or more guide blocks (e.g., guide block 301) may alsobe attached to one or more retaining members or rings (e.g., retainingring 400) as best depicted in FIGS. 14 and 16 for example, to allowautomatic welding of opening 120.

Guide block 301 includes a weld area slot 310 located radially adjacentto opening 120, when block 300 is inserted in slot 21 as depicted inFIGS. 12, and 14-17 for example, By inserting a plurality of guideblocks (e.g., guide block 301) into a plurality of slots (e.g., slot 21)of rotor 10, a continuous circumferential welding groove 355 (i.e.,formed by a plurality of slots 310 aligned circumferentially), bestshown in FIG. 16, is created around rotor 10. Such circumferentialgroove allows for automatic welding by forming a continuouscircumferential geometry, i.e., by eliminating the intermittent geometryof the grooves (e.g., groove 21) between the bridge rails at both axialsides of the machined cutout.

After the plurality of guide blocks (e.g., guide block 301) is insertedinto the plurality of slots (e.g., slot 21) of rotor 10, the retainingrings (e.g., retaining ring 400) are placed around rotor 10 and adjacentto the guide blocks (e.g., guide block 301) and bridge rails 20 (e.g.,bridge rail 22 and 23) at both axial ends thereof as depicted in FIGS.14-17, The guide blocks (e.g., guide block 301) are welded (or otherwisecoupled) to the retaining rings (e.g., retaining ring 400) at ends ofthe guide blocks, creating a continuous rigid support structure asdepicted in FIG. 14, for example. A guide block weld preparation 327(FIG. 14) may be machined into the axial faces of the guide blocks(e.g., guide block 301)) and rail weld preparations (not shown) may bemachined into the axial faces of the bridge rails (e.g., bridge rail 22and 23) to allow such welding. As will be understood by those skilled inthe art, a weld preparation may include a shape and/or or textureapplied to a receiving surface to promote proper fusion of the weld tothe surface to which the weld is to be applied.

The coupling of the guide blocks (e.g., guide block 301) with theretaining rings (e.g., retaining ring 400) aid in the ease of weldpreparation machining by providing rigidity during the machining andsubsequent welding process. In particular, the rigidity providedmaintains a guide block stationary during any machining required toprepare guide block 301 for welding, i.e., to create guide block weldpreparation 327 (FIG. 14). Such rigidity may inhibit or prevent “pull”(i.e., weld shrinkage experienced during the cooling and solidificationof the newly applied weldment) on the guide blocks that is associatedwith welding as will be understood by those skilled in the art.

Once such a weld preparation (e.g., weld preparation 327, FIG. 14) iscomplete, one or more backing bands (e.g., backing band 350) may beplaced at an inner diameter of continuous circumferential groove 355formed by the plurality of weld area slots (e.g., weld area slot 310) inbridge rails 20 to close circumferential groove 21 including opening 120as depicted in FIGS. 15-17, for example, The backing band(s) (e.g.,backing band 350) are machined with a correct weld preparation androlled/formed to a desired shape prior to installation such that thebacking bands are configured (e.g., shaped and dimensioned) to bereceived in the continuous circumferential welding groove 355 and tocover circumferential groove 121 including opening 120.

Guide block 301 may have a positioning ledge 315 to aid in the radialplacement of the backing bands (e.g., backing band 350). Positioningledge 315 is located only in the center of slot 310 and is axiallyseparated from opposed sides of slot 310 by spaces 312, as best depictedin FIG. 15, to prevent or inhibit backing band 350 from fusing to abottom 321 of weld area slot 310 during the welding process. This isaccomplished by placing sufficient distance between positioning ledge315 and bottom 318. The backing bands are welded in position, e.g. viaone or more root welds 360 to opposite sides of slot 310 (e.g., weldpreparations 327), as depicted in FIG. 15. This installation creates a360 degree radial groove (e.g., welding groove 355, FIG. 16) whichallows for either automatic or manual welding.

For example, rotor 10 may be rotated and groove 355 may he automaticallywelded using automatic TIG (Tungsten Inert Gas) welding during, suchrotation. As depicted in FIG. 20, a support frame 500 may support awelding arm 510 aligned such that a tip 520 thereof is adjacent towelding groove 355 to allow welding thereof as rotor 10 rotates. Suchwelding support frame 500 and welding arm 510 may be configured toperform automatic TIG welding. In particular, a weld (e.g., a weld 550)may be formed by a process of weld metal being deposited continuouslyabout the surface of a rotor (e.g., rotor 10) as the rotor rotates untila sufficient height of weld material is reached, such as the height ofrails 20. For example, weld 550 may result from such automatic weldingand may fill circumferential groove 355 as depicted in FIG. 17.

As described above and depicted in FIG. 16, guide block 301 may bereceived in bridge rail slot 21 between bridge rail 22 and bridge rail23 such that guide block 300 extends over circumferential groove 121including opening 120. A second guide block 600 may be received in asecond rail slot 610 adjacent to, and similar for slot 21. Backing band350 may be received in a weld area slot (e.g., weld area slot 310) ofthe adjacent guide blocks (e.g., guide block 301 and guide block 604 Agroove portion 620 of circumferential groove 121 locatedcircumferentially adjacent slot 21 and immediately adjacent rail 22 maythereby be covered by backing band 350 for example. Further, instead ofthe automatic welding described above, manual welding is possible duringthe rotation of, or without rotating, rotor 10.

After welding (e.g., weld 550 (FIG. 17)) and any required heat treatment(e.g., heat treatment to provide a required microstructure and materialproperties in the weldment, heat affected zone (HAZ) and adjacent parentmetal to allow for the safe future operation of the component beingrepaired) are complete, it is necessary to remove the welding supportstructure (e.g., retaining ring 400 and guide block 301). The retainingrings may be removed first, particularly if they are to be re-used forfuture repairs. This is accomplished by machining the outer diameter ofthe guide blocks (e.g., guide block 301) and bridge rails (e.g., bridgerail 22 and bridge rail 23) using standard commercially available lathecutting tool, for example. Such machining removes the welds to theretaining rings while it restores the outer diameter of the weld repairback to the desired original geometry of bridge rails 20. The retainingrings are freed from the assembly and removed.

As depicted in FIGS. 14 18 and 19, guide block 301 includes one or morebreakaway cuts (e.g., breakaway cut 319) axially spaced from slot 310 onboth ends of slot 310, Breakaway cut 319 is a space between adjacentportions (e.g., an inner portion 325 and an outer portion 326) of guideblock 301, which extends around guide block 301 and which extends to acore 322 of guide block 301. Core 322 is located at a central interiorportion of guide block 301, at a distance from an outer surface 323 ofguide block 301. Core 322 connects inner portion 325 and outer portion326 of guide block 301. A space (i.e., breakaway cut 319) may extendcompletely around core 322 such that inner portion 325 and outer portion326 are connected only by core 322. Thus, core 322 is also spaced froman adjacent surface (e.g., sides and bottom) of bridge rail slot 21(FIG. 16), when received in slot 21 (FIG. 16). Also, breakaway cut 319may be aligned approximately parallel with the one of weld preparations327 closest thereto when received in slot 21. Breakaway cut 319 may beplaced an appropriate longitudinal distance (relative to guide block301) away from the one of weld preparations 327 closest thereto toprevent the weld (e.g., weld 550) being applied to slot 310 frompenetrating into breakaway cut 319

Guide block 301 also includes a second core 322, connecting an outerportion 328 and an inner portion 324, and a second breakaway cut 329.Guide block 301 may be machined, for example, rough milled axially usinga standard commercially available end mill (not shown) selected based,on the base material being machined to a depth such that core 322 andsecond core 322 are removed as depicted in FIG. 19. The breakaway cuts(e.g., breakaway cut 319 and second breakaway cut 329) allow outerportion 326 and outer portion 328 to be separated from inner portion asdepicted in FIG. 19 when the cores are removed, because the coresprovide the only connection therebetween. Thus, the breakaway cuts mayallow for rapid machine removal (e.g., using an end mill (not shown) ofthe guide blocks and provide a buffer space that protects againstaccidental machining of the original component's surface geometry. Forexample, it is not necessary for any machining tool to approach thebottom of slot 21 (FIG. 16) since the bottom of the cores are spacedfrom the bottom of the slots due to the breakaway cuts (e.g., breakawaycut 319 and second breakaway cut 329) and the tool can stop machiningwhen the cores are removed i.e., at a distance from the bottom surfaceof slot 21 (FIG. 16). Such machining to remove the cores is referredherein as “rough” machining.

Accordingly, a remaining portion 333 of guide block 301 remains attached(e.g., via a remaining portion of weld 550, FIG. 17) to bridge rail slot21 after the removal of outer portion 326 and outer portion 328 via“rough” machining. Such “rough” machining may also remove backing band350 from weld area slot 310. The removal of backing band 350 may befacilitated by the attachment of backing band 350 to side wall(s) ofslot 310 (e.g., weld preparation 327) via the root weld described aboveto weld area slot 310. In particular, the spaces on opposite sides ofledge 315 inhibit fusion of backing band 350 and ledge 315 which wouldmake removal of backing band 350 more difficult.

Remaining portion 333 may be machined to return bridge rail slot 21 to ageometrical configuration as existed prior to the beginning of therepair using rotating machine tools (e.g., modified and taper profiledend mill 650 (FIG. 21) and/or a profile style milling tool 651 (FIG.22)) Such machining is facilitated, because the original geometry ofbridge rail slot 21 remains on both sides of the welded section (i.e.,remaining portion 330), which may be used as a reference. The lack ofattachment of outer portion 328 and outer portion 326 to slot 21 (e.g.,by lack of welding in contrast to remaining portion 333) allows theareas of slot 21 previously occupied by outer portion 328 and outerportion 326 to provide such reference for machining remaining portion333. Also, the reduced amount of support structure material (e.g., outerportion 328 and outer portion 326), which requires removal by finemachining (e.g., using modified and tapered profiled end mill 650 and/orprofile style milling tool 651), resulting from removing outer portion326 and outer portion 328, may result in reduced final machining time.The amount remaining to be machined away by such fine machining istypically between 0.050″-0.100″ on a side (e.g., less than 5% of thetotal guide block thickness). This amount may differ based on theexperience and comfort level of the machinist doing the work. Forexample, a more experienced machinist may perform rough machining to agreater depth thereby leaving less final machining to be performed.

In an alternate unillustrated embodiment, breakaway cuts may extend onlyunder a bottom portion of guide block 301 (i.e., not completely aroundcore as illustrated in FIG. 18). In this embodiment, when a portion ofthe guide block above such a breakaway cut is removed by machining asdescribed above, an outer portion would be freed from an inner portion.

In another embodiment depicted in FIG. 3, it may be desired to weld anentire outer portion of a cylinder 700 except for slots 710. Guideblocks 720 may be inserted fully or partially into such slots. A weld(not shown) may then be applied to an outer surface 730 thereby coveringslot 710 by automatic or manual welding, Guide blocks 720 may alsoinclude machining cutouts 740, which are complementary relative to slots710 and thereby allow guide blocks 720 to be inserted into slots 710.Similar to the machining. of the guide blocks described above, the weldapplied to the top portion of guide block 720 and/or all or part ofguide block 720 itself, may be machined away such that guide block 720may be easily removed thereby ensuring access to slot 710 after thewelding is complete. For example, cylinder 700 may be a typicalrotating-type shad with keyway slots (e.g., slots 710) shown. Often, thesurfaces of the shafts require weld build up and the key slots makewelding using automatic processes difficult if not impossible. The useof the guide blocks allows for the continuous welding of the surfaceusing automatic or manual welding processes as described above for rotor10. The cutouts allow for the re-establishment of the key slots by rapidremoval of the guide blocks.

Further, the guide blocks (e.g., guide block 301), backing bands (e.g.,backing band 350), and/or retaining rings (e.g., retaining rings 400)may be used in any of various geometries to allow automatic welding ofany openings created in a surface. For example, the guide blocks may beutilized with the backing bands or by themselves in round or fiatgeometries to allow for such automatic welding. Also, the guide blocks,backing bands, and/or retaining rings may be utilized to join not onlydiscontinuous geometries of a single component, but also to joinmultiple components containing both continuous and discontinuousgeometries at the required connection interfaces between suchcomponents.

Further, such guide blocks allow for the continuous welding of roundcomponents with discontinuous geometries in a “horizontal” turningmechanism i.e., in contrast to the vertical orientation described aboverelative to rotor 10. This reduces the required weld times and makes thewelding repair process (e.g., manual or automatic) capable of beingperformed within the rotational time constraints required to preventbowing of the component(s). For example, rotors and shafts will sag(e.g., bow) when supported on the ends thereof and heat is applied. Thesag or deflection of the rotor may become progressively worse over timeif the shaft or rotor is not rotated. There is a minimal rotationalspeed required to prevent the sag of these components. The timerestraints of rotation and the rotation speeds are based on thecomponent's length, weight, material and other physical andmetallurgical characteristics.

Also, the guide blocks allow for direct heat treatment application toround components, e.g. shafts and rotors, during the welding process.For example, electric resistance type heaters (e.g., stationary andsliding) require direct contact with the surface being heated. The guideblocks as discussed above create a continuous outer surface for theapplication of these heating elements, The once discontinuous geometryon the outer surface of round components are made quasi-continuous bythe guide blocks, and this application of surface riding heating andmonitoring equipment may he utilized, as will be understood by thoseskilled in the art.

Also, the support ledges (e.g., positioning ledge 315) described aboveas supporting the backing bands could also support other supportmechanisms such as ceramic backers or chill rings as will be understoodthose skilled in the art. It will be understood by one skilled in theart that the above described systems and methods for repairing cracksmay be applied to rotors of any type of turbines (e.g., steam turbines,gas turbines), other rotating rotors or shafts, or other objectssubjected to stresses similar to those found in a turbine environment,which have cavities therein and/or cracking in the walls of suchcavities.

Although preferred embodiments have been depicted and described indetail herein, it will be apparent to those skilled in the relevant artthat various modifications, additions, substitutions and the like can bemade without departing from the spirit of the invention and these aretherefore considered to be within the scope of the invention as definedin the following claims.

1. A method for use in closing an opening in a rotor, the methodcomprising: providing a rotor having an internal circumferentiallyclosed groove bounded by a circumferential portion of the rotor;removing a part of the circumferential portion of the rotor to create anopening to provide access to the groove; and machining curved sidewallsin the groove immediately adjacent the opening to lower a stress of atop end of the groove during operation.
 2. The method of claim 1 whereinthe curved sidewalls connect sidewalls of the groove to sides of theopening.
 3. The method of claim 1 further comprising inserting a toolthrough the opening and machining the groove to form the curvedsidewalls
 4. The method of claim 1 further comprising inserting a toolthrough the opening and machining the groove to form sidewalls of thegroove.
 5. The method of claim 1 further comprising filling in theopening.
 6. The method of claim 5 wherein the filling in the openingcomprises covering the groove by welding the opening.
 7. The method ofclaim 6 wherein the welding causes a heat affected zone of the groove tohe moved relative to the location of the zone prior to the removing thepart of the circumferential portion.
 8. The method of claim 6 furthercomprising machining a portion of a weld formed by the welding to returnthe at least one bridge rail to an original geometry prior to theopening being created.
 9. The method of claim 6 further comprisingmachining the rotor such that a geometry of an outer circumferentialsurface of the rotor has a substantially same geometrical configurationafter the welding as prior to the removing the part of thecircumferential portion.
 10. The method of claim 7 wherein the moving ofthe heat affected zone comprises moving the heat-affected zone from thepart of the circumferential portion to the curved sidewalls.
 11. Themethod of claim 1 wherein the part of the circumferential portioncomprises at least a portion of a bridge rail of the rotor.
 12. Themethod of claim 1 wherein the groove comprises a portion of an L-grooveconfigured to cool the rotor.
 13. The method of claim 1 wherein thecreating the opening comprises creating the opening offset fromsidewalls of the groove.
 14. The method of claim 1 wherein the groovecomprises a radial portion of the groove aligned substantially radiallyrelative to the rotor.
 15. The method of claim 1 further comprisinginserting a tool through the opening and machining the groove to form abottom of the groove.
 16. The method of claim 1 further comprisingmachining an end of the groove furthest from the opening to remove atleast one crack therein.